In this revised application, we have taken the recommendations from the reviewers by focusing specifically on the development of anti-b2-Microglobulin (b2-M) antibody as a therapeutic agent for the treatment of human prostate cancer bone metastasis. In addition, we also provided new information on a putative b2-M receptor, a novel strategy exploiting b2-M-receptor mediated cell signaling mechanisms and combinatorial approach achieving synergism between anti-b2-M monoclonal antibody (mAb) plus radiation as a promising therapeutic regimen for prostate cancer bone metastases. The hypothesis of this proposal is that anti-b2-M mAb interferes with HFE (a hereditary hemochromatosis associated gene)-TFRC (Transferrin Receptor)-TF (Transferrin) complex and iron transport, thus provokes downstream redox signaling changes with microRNAs (miRNAs) serving as regulators for a series of cell stress response proteins and DNA repair enzymes that ultimately trigger cell death in cancer but not normal cells. Two Specific Aims are proposed in this revised application. Specific Aim 1: to develop anti-b2-M mAb as a therapeutic antibody for prostate cancer bone metastasis therapy using experimental human prostate cancer xenograft and transgenic mouse models, evaluate antibody toxicity in mice, and determine the synergistic interaction between anti-b2-M mAb plus ionizing radiation on the growth of prostate cancer cells and tumors. This Aim is based on our discovery that b2-M is a major growth factor and pleiotropic signaling molecule that confers the growth, survival, and epithelial to mesenchymal transition (EMT) of human prostate cancer cells. Successful accomplishment of this Aim will allow accelerated translation of targeting b2-M as a novel therapeutic approach for human prostate cancer bone metastasis. Specific Aim 2: to evaluate and validate a putative b2-M receptor, a non-classical major histocompatibility complex (MHC)-like molecule, the hereditary hemochromatosis associated gene, HFE. The functional role of HFE and its relationship to TFRC-TF complex, iron uptake, reactive oxygen species (ROS) production, DNA damages, and cell death will be assessed. In this aim, we will investigate the function of anti-b2-M mAb on TFRC-TF complex that could promote iron uptake via endosomal iron recycling, production of ROS and highly reactive hydroxy radicals that could cause DNA damages in cancer but not normal cells. Regulation of miRNAs, potential downstream targets of redox signaling, on cell stress response proteins and DNA repair enzymes will be specially emphasized. In summary, this revised application carefully follows the recommendations of the reviewers to develop novel approaches for targeting b2-M-mediated downstream growth and signaling pathways in human prostate cancer, which has exciting potential for clinical translation to manage prostate cancer bone metastasis. PUBLIC HEALTH RELEVANCE: Prostate cancer bone metastasis contributes to mortality and morbidity of prostate cancer patients. We have developed a new therapeutic approach by using a novel anti-b2-Microglobulin antibody plus radiation, which has been shown to completely abolish the growth of human tumors in mice. This project focuses on defining the molecular mechanism of this synergism and the appropriate preclinical studies to move these discoveries from bench to the bedside.